In such heat exchangers, the weight of the lengths of tube disposed in the middle portions would cause deformation if the weight were not transferred to the outer lengths which are connected to the inlet or the outlet. Proposals have already been made to transfer the weight by rigidly interlocking together all of the lengths of tube in a top zone by means of small round or square members welded between the lengths. In addition to the weight of the tubes, this rigid assembly is subjected to stresses due to:
differences in expansion between different loops since their average temperatures are different because the fluid flowing along the tubes from the inlet to the outlet is being heated;
vibrations that may arise in operation;
swinging phenomena of entire panels of tubes inside the combustion chamber; and
weld shrinkage since the welding was performed on a rigid structure.
These stresses can lead to deformation, cracking and even breakage of some of the welds.
Proposals have been made in French patent specification No. 1 259 288 for a system of interlocking adjacent tubes in a heat exchanger, the system comprising a male member welded to one of the adjacent tubes, engaging and locking with two female members welded to the other tube.
Another proposal has been made in U.S. Pat. 2 809 616 for a system of interlocking adjacent tubes in a heat exchanger, the system comprising three junction members on each side of the two adjacent tubes, the middle member being welded to one of the tubes and the other two being placed respectively above and below the middle member and being welded to the other tube. These members are joined by a vertical pin passing therethrough.
Such systems are relatively complex. In the case of French specification No. 1 259 288 they require different complex shaped parts, and in the case of U.S. Pat. No. 2 809 616 a total of eight parts and six welds are required.
Preferred embodiments of the present invention provide a system for interlocking lengths of vertical tube to transfer the weight of the middle tubes to the inlet and outlet tubes, said preferred systems not only avoid stresses that are likely to cause deformation, cracking, or breakage of the welds, they are also simple to implement and can be installed rapidly.